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Cheng P.,Shanghai JiaoTong University | Alberts I.,City University of New York | Li X.,NY State Institute for Basic Research in Developmental Disabilities
International Journal of Developmental Neuroscience | Year: 2013

Extracellular signal regulated kinases (ERK) are important components of the Ras-Raf-MEK-ERK signaling pathway cascades that mediate intracellular stimuli transduction and gene expression. ERK1 (44. kDa) and ERK2 (42. kDa) are homologous subtypes of the ERK family, which participate in regulation of a variety of cell activities, including cell proliferation, migration and differentiation, especially in the central nervous systerm (CNS). Hence, they exert critical effects on neuron and astrocyte development. Astrocytes are critically involved in maintaining CNS homeostasis and supporting neuron growth. When exposed to an extracellular stimulus, such as inflammation or oxidative stress, the corresponding cell response can be regulated by the ERK1/2 signaling pathway. Furthermore, several lines of evidence have demonstrated a correlation between astrocyte activity and the Ras-Raf-MEK-ERK signaling pathway. However many questions remain unanswered regarding the role of ERK1/2 in astrocyte development. This review summarizes the possible role of ERK1/2 signaling cascades in modulating the proliferation, differentiation and apoptosis of astrocytes in both physiological and pathological conditions. In addition, this review also briefly elucidates the participation of ERK1/2 in the process of human brain glia tumor oncogenesis and metastasis, which will provide some concepts for treatment strategies to delay the process of tumor evolution. © 2013 ISDN. Source

Wei H.,Central Laboratory | Mori S.,Johns Hopkins University | Hua K.,Johns Hopkins University | Li X.,NY State Institute for Basic Research in Developmental Disabilities
International Journal of Developmental Neuroscience | Year: 2012

Abnormal neuroimmune responses have been reported to be associated with autism and could be appropriate targets for pharmacologic intervention. Our previous studies showed that neuroimmune factor, interleukin (IL)-6, was significantly elevated in the fontal cortex and cerebellum of autistic subjects. The IL-6 overexpressing mice displayed several autism-like features as well as an abnormal dendritic spine morphology and synaptic function. The purpose of this study was to examine the volumetric differences in the brain of IL-6 overexpressing mice and compare with corresponding control mice using magnetic resonance imaging. Here we show that IL-6 overexpressing mice display an increase in the total brain volume. In addition, the lateral ventricle is also enlarged in the IL-6 overexpressing mice. The brain structures surrounding the lateral ventricle were squeezed and deformed from the normal location. These results indicate that IL-6 elevation in the brain could mediate neuroanatomical abnormalities. Taking together with our previous findings, a mechanism by which IL-6 may be involved in the pathogenesis of autism is proposed. © 2012 ISDN. Source

Xu N.,Hunan Childrens Hospital | Li X.,NY State Institute for Basic Research in Developmental Disabilities | Zhong Y.,Hunan Childrens Hospital
Mediators of Inflammation | Year: 2015

Autism is a disorder of neurobiological origin characterized by problems in communication and social skills and repetitive behavior. After more than six decades of research, the etiology of autism remains unknown, and no biomarkers have been proven to be characteristic of autism. A number of studies have shown that the cytokine levels in the blood, brain, and cerebrospinal fluid (CSF) of autistic subjects differ from that of healthy individuals; for example, a series of studies suggests that interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) are significantly elevated in different tissues in autistic subjects. However, the expression of some cytokines, such as IL-1, IL-2, transforming growth factor-β (TGF-β), and granulocyte-macrophage colony-stimulating factor (GM-CSF), is controversial, and different studies have found various results in different tissues. In this review, we focused on several types of proinflammatory and anti-inflammatory cytokines that might affect different cell signal pathways and play a role in the pathophysiological mechanism of autistic spectrum disorders. © 2015 Ningan Xu et al. Source

Yang K.,New Hill | Yang K.,Qingdao University | Cao F.,New Hill | Sheikh A.M.,New Hill | And 5 more authors.
Brain Structure and Function | Year: 2013

The Ras/Raf/ERK1/2 signaling pathway controls many cellular responses such as cell proliferation, migration, differentiation, and death. In the nervous system, emerging evidence also points to a death-promoting role for ERK1/2 in both in vitro and in vivo models of neuronal death. Recent studies have suggested that abnormal apoptosis in the central nervous system may be involved in the pathogenesis of autism. Two studies reported that both a microdeletion and microduplication on chromosome 16, which includes the MAPK3 gene that encodes ERK1, are associated with autism. In addition, our recent work showed that Ras/Raf/ERK1/2 signaling activities were significantly up-regulated in the frontal cortex of autistic individuals and in the BTBR murine model of autism. To further investigate how Ras/Raf/ERK1/2 up-regulation may lead to the development of autism, we developed a cellular model of Raf/ERK up-regulation by over-expressing c-Raf in cultured cortical neurons (CNs) and cerebellar granule cells (CGCs). We found that Raf/ERK up-regulation stimulates the migration of both CNs and CGCs, and impairs the formation of excitatory synapses in CNs. In addition, we found that Raf/ERK up-regulation inhibits the development of mature dendritic spines in CNs. Investigating the possible mechanisms through which Raf/ERK up-regulation affects excitatory synapse formation and dendritic spine development, we discovered that Raf/ERK up-regulation suppresses the development and maturation of CNs. Together, these results suggest that the up-regulation of the Raf/ERK signaling pathway may contribute to the pathogenesis of autism through both its impairment of cortical neuron development and causing neural circuit imbalances. © 2012 Springer-Verlag. Source

Gilbert M.E.,U.S. Environmental Protection Agency | Ramos R.L.,New York Institute of Technology | Mccloskey D.P.,CUNY - College of Staten Island | Goodman J.H.,NY State Institute for Basic Research in Developmental Disabilities | Goodman J.H.,SUNY Downstate Medical Center
Journal of Neuroendocrinology | Year: 2014

Thyroid hormones (TH) play crucial roles in brain maturation and are important for neuronal migration and neocortical lamination. Subcortical band heterotopia (SBH) represent a class of neuronal migration errors in humans that are often associated with childhood epilepsy. We have previously reported the presence of SBH in a rodent model of low level hypothyroidism induced by maternal exposure to the goitrogen, propylthiouracil (PTU). In the present study, we report the dose-response characteristics of this developmental malformation and the connectivity of heterotopic neurones with other brain regions, as well as their functionality. Pregnant rats were exposed to varying concentrations of PTU through the drinking water (0-10 p.p.m.) beginning on gestational day 6 to produce graded levels of TH insufficiency. Dose-dependent increases in the volume of the SBH present in the corpus callosum were documented in the adult offspring, with a clear presence at concentrations of PTU that resulted in minor (< 15%) reductions in maternal serum thyroxine as measured when pups were weaned. SBH contain neurones, oligodendrocytes, astrocytes and microglia. Monoaminergic and cholinergic processes were prevalent and many of the axons were myelinated. Anatomical connectivity of SBH neurones to cortical neurones and the synaptic functionality of these anatomical connections was verified by ex vivo field potential recordings. SBH persisted in adult offspring despite a return to euthyroid status on termination of exposure and these offspring displayed an increased sensitivity to seizures. Features of this model are attractive with respect to the investigation of the molecular mechanisms of cortical development, the effectiveness of therapeutic intervention in hypothyroxinaemia during pregnancy and the impact of the very modest TH imbalance that accompanies exposure to environmental contaminants. © Published 2014. This article is a U.S. Government work and is in the public domain in the USA. Source

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